1. Technical Field
Bioabsorbable copolymers having units derived from tricarboxylic acids and triols are described herein. Surgical articles are made from such copolymers including articles for promoting the growth of soft tissue.
2. Background of the Related Art
Polymers having units derived from citric acid have been described for various purposes. For example, U.S. Pat. No. 3,661,955 discloses polyesters of citric acid and sorbitol useful as intermediates in the manufacture of medicine, emulsifiers and as additives to yeast raised products. As another example, U.S. Pat. No. 5,026,821 discloses hydrophilic polymers composed of polyamides resulting from the condensation of citric acid with diamines. The polymers are employed as carriers or reservoirs for the controlled release of drugs, as sutures, surgical prostheses, and surgical adhesives. However, these patents do not describe copolymers including monomeric units derived from tricarboxylic acid and monomeric units derived from a triol, wherein the copolymer includes a substituent which provides a net surface charge.
It has been postulated that the presence of a net surface charge on certain substances can promote wound healing. For example, U.S. Pat. Nos. 4,988,358 and 5,092,883 disclose beads having chemically induced surface charges for promoting tissue growth which are produced by attaching functional groups to a dextran matrix. As another example, Patent No. WO 88/01155 discloses biomaterial implants derived from glutaraldehyde-treated animal tissue covalently bonded to a compound which imparts a net charge to the implant to prevent detrimental calcification of the implant. These publications likewise do not describe copolymers which include a proportion of monomeric units derived from a tricarboxylic acid and a proportion of monomeric units derived from a triol. Nor is the addition of a charge inducing substituent to such copolymers described.